Made up mainly of water, which represents approximately 92% of its weight, plasma is made up of many substances, including:
55% of the total circulating blood is made up of plasma.
The concentration of the aqueous component is maintained within a range of constant values thanks to the intake of liquids in the diet and through the control of their excretion at the renal level.
The protein fraction of the blood is mainly made up of albumins (4.5 grams per 100ml), globulins (2.7 grams per 100 ml) and fibrinogen (2.25 grams per 100ml).
|Functions of plasma proteins|
|Albumins||Liver||They maintain the colloid-osmotic pressure of the blood by promoting the passage of water from the interstitial fluid to the capillaries; they bind and transport numerous substances in the plasma: hormones, drugs, bilirubin, etc.|
|Globulins||Liver and lymphoid tissue||They are divided into three fractions: α, Β and γ. The first two cover transport functions, while the third includes the immunoglobulins involved in the body’s defense processes (antibodies produced by plasma cells). Transferrin, for example, belongs to the Beta class and acts as an iron transporter in the plasma.|
|Fibrinogen||Liver||It is a large protein molecule that is involved in the blood clotting process.|
Blood plasma, due to the richness of its components, can be used instead of whole blood in situations where there is a rapid loss of fluids with a reduction in circulating volume (burns, trauma). The sampling operation is called plasmapheresis and is also useful for replacing plasma rich in harmful substances with healthy plasma from a donor; the latter can also be used by the pharmaceutical industries to isolate the various components and use them in the treatment of numerous pathologies (immunological, hepatic, renal and haemorrhagic).